Avoid setting children's parent twice

parso/parser.py

@@ -23,7 +23,7 @@
 complexity of the ``Parser`` (there's another parser sitting inside
 ``Statement``, which produces ``Array`` and ``Call``).
 """
-from typing import Dict
+from typing import Dict, Type
 
 from parso import tree
 from parso.pgen2.generator import ReservedString
@@ -110,10 +110,10 @@ class BaseParser:
     When a syntax error occurs, error_recovery() is called.
     """
 
-    node_map: Dict[str, type] = {}
+    node_map: Dict[str, Type[tree.BaseNode]] = {}
     default_node = tree.Node
 
-    leaf_map: Dict[str, type] = {}
+    leaf_map: Dict[str, Type[tree.Leaf]] = {}
     default_leaf = tree.Leaf
 
     def __init__(self, pgen_grammar, start_nonterminal='file_input', error_recovery=False):
@@ -156,8 +156,6 @@ def convert_node(self, nonterminal, children):
             node = self.node_map[nonterminal](children)
         except KeyError:
             node = self.default_node(nonterminal, children)
-        for c in children:
-            c.parent = node
         return node
 
     def convert_leaf(self, type_, value, prefix, start_pos):

parso/python/parser.py

@@ -96,8 +96,6 @@ def convert_node(self, nonterminal, children):
                 # prefixes. Just ignore them.
                 children = [children[0]] + children[2:-1]
             node = self.default_node(nonterminal, children)
-        for c in children:
-            c.parent = node
         return node
 
     def convert_leaf(self, type, value, prefix, start_pos):
@@ -185,8 +183,6 @@ def _stack_removal(self, start_index):
 
         if all_nodes:
             node = tree.PythonErrorNode(all_nodes)
-            for n in all_nodes:
-                n.parent = node
             self.stack[start_index - 1].nodes.append(node)
 
         self.stack[start_index:] = []

parso/python/tree.py

@@ -553,8 +553,6 @@ def __init__(self, children):
         for child in parameters_children:
             if isinstance(child, Param):
                 input_has_param = True
-                # Fix parent relationship of Param children.
-                child.parent = parameters
         # If input parameters list already has Param objects, keep it as is;
         # otherwise, convert it to a list of Param objects.
         if not input_has_param:
@@ -666,8 +664,6 @@ def __init__(self, children):
         for child in parameters_children:
             if isinstance(child, Param):
                 input_has_param = True
-                # Fix parent relationship of Param children.
-                child.parent = self
         # If input children list already has Param objects, keep it as is;
         # otherwise, convert it to a list of Param objects.
         if not input_has_param:
@@ -1102,8 +1098,6 @@ class Param(PythonBaseNode):
     def __init__(self, children, parent=None):
         super().__init__(children)
         self.parent = parent
-        for child in children:
-            child.parent = self
 
     @property
     def star_count(self):

test/test_dump_tree.py

@@ -163,3 +163,20 @@ def test_dump_parser_tree_invalid_args():
 
     with pytest.raises(TypeError):
         module.dump(indent=1.1)
+
+
+def test_eval_dump_recovers_parent():
+    module = parse("lambda x, y: x + y")
+    module2 = eval(module.dump())
+    assert module2.parent is None
+    lambda_node = module2.children[0]
+    assert lambda_node.parent is module2
+    assert module2.children[1].parent is module2
+    assert lambda_node.children[0].parent is lambda_node
+    param_node = lambda_node.children[1]
+    assert param_node.parent is lambda_node
+    assert param_node.children[0].parent is param_node
+    assert param_node.children[1].parent is param_node
+    arith_expr_node = lambda_node.children[-1]
+    assert arith_expr_node.parent is lambda_node
+    assert arith_expr_node.children[0].parent is arith_expr_node